The following discussion assumes that the reader is familiar with the IETF RFC 1889 standard—RTP: A Transport Protocol for Real-Time Applications and with the IETF RFC 1890 standard—RTP Profile for Audio and Video Conferences with Minimal Control.
Real-time transport protocol (RTP), as defined in the RFC 1889 standard, provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. These transport functions provide end-to-end delivery services for data with real-time characteristics, such as interactive audio and video. Such services include payload type identification, sequence numbering, time stamping and delivery monitoring. RTP supports data transfer to multiple destinations using multicast distribution if provided by the underlying network.
The RFC 1889 standard does not provide any mechanism to ensure timely delivery or provide other quality-of-service guarantees, but relies on lower-layer services to do so. It does not guarantee delivery or prevent out-of-order delivery, nor does it assume that the underlying network is reliable and delivers packets in sequence. The sequence numbers included in RTP allow the receiver to reconstruct the sender's packet sequence, but sequence numbers might also be used to determine the proper location of a packet, for example in video decoding, without necessarily decoding packets in sequence.
A typical application of RTP involves streaming data, where packets of Advanced Systems Format (ASF) audio-visual (AV) data is sent in RTP packets over a network from a server to a client or peer-to-peer. The ASF audio and video data can be stored together in one ASF packet. As such, an RTP packet can contain both audio and video data.
RTP, as defined the RFC 1889 standard, lacks flexibility to group multiple payloads together into a single RTP packet, and to split a payload across multiple RTP packets. Neither does the RFC 1889 standard define a format in which metadata can be delivered with each payload in an RTP packet. Another deficiency of the RFC 1889 standard is the lack of a mechanism for streaming encrypted blocks of data across a network while maintaining a block boundary of each encrypted block such that the recipient thereof can decrypt the encrypted blocks of data. In would be an advance in the art to provide such flexibility as an enhancement to RTP streaming. Consequently, there is a need for improved methods, computer-readable medium, data structures, apparatus, and computing devices that can provide such flexibility.